The present invention relates to a technology which stabilizes radiation detection characteristics of a radiation tomographic imaging apparatus.
It has been known that the radiation detection characteristics of a radiation tomographic imaging apparatus depend on the temperature of a detecting element in a radiation detecting apparatus therefor, particularly a photoelectric conversion element. On the other hand, the temperature of the detecting element has a strong tendency to gradually increase due to the generation of heat of electrical/electronic components disposed around the detecting element. Therefore, generally, a cooling system is provided in the radiation detecting apparatus to cool heating components or the like and control the temperature of a detecting element to be kept constant as much as possible, thereby achieving stabilization of the radiation detection characteristics.
As the cooling system mentioned above, an air cooling system using a cooling fan has been known. That is, wind is generated by the cooling fan, and the wind is applied to a substrate provided with detecting elements and a radiator disposed on the substrate, etc. to perform cooling. This system has heretofore been used because it is simple in structure and relatively easy to construct (refer to, for example, a Japanese Patent Laid-Open No. 2004-57834).
However, the generation of heat of the electrical/electronic components is often done in the vicinity of the detecting elements. Therefore, the heat is liable to be conducted to the detecting elements, and the control on the temperature of each detecting element often won't go as hoped in the cooling system.
The direction and volume of wind entering inside from the outside of the radiation detecting apparatus depend greatly on the rotational speed of a gantry rotating section equipped with the radiation detecting apparatus. Therefore, when the rotational speed of the gantry rotating section is changed, the temperature of the detecting element is also liable to change. That is, the cooling method using the cooling fan is not capable of sufficiently suppressing the change in the temperature of the detecting element and is difficult to achieve the stabilization of the detection characteristics.
With the foregoing situation in view, there has been a demand for a technology capable of when each detecting element of the radiation detecting apparatus in the radiation tomographic imaging apparatus is cooled, suppressing a change in the temperature of the detecting element and stabilizing detection characteristics.